If a flame is present at sensor and a reading of 0 µ Adc is obtained , check for a secondary ground connection to the 25 V ( GND ) terminal . If secondary connection exists , temporarily remove connection and measure flame current .
LOW OR UNSTEADY FLAME CURRENT
If the current to the S87 flame circuit is less than 1.5 µ Adc or is unsteady , check the burner flame , flame sensor location and electrical connections as follows .
BURNER FLAME
The flame sensor must be constantly immersed in flame . Check burner flame conditions as shown in Figure 14 . Flame Sensor The flame signal is best when about 1 inch of flame rod is immersed in the burner flame . A bent flame rod bent mounting bracket or cracked ceramic insulator can affect flame signal . Replace flame sensor if necessary .
ELECTRICAL CONNECTIONS AND SHORTS
Connections at the flame sensor must be clean and tight . If wiring needs replacement , use moisture-resistant No . 18 wire rated for continuous duty up to 221 ° F . Hot Surface Ignitor- Sensor Circuit Controls like the S89C provide AC power to the igniter / sensor and then shutoff the 120 Vac to allow the ignitor / sensor to send the flame current back to the control . The flame signal back to the S89C should be at least 0.8 microamps DC (µ Adc ) or the system will lock out .
The HSI is powered with 120 Vac during pre-purge so a microammeter with a shunt switch must be used to test flame signal or the meter will be damaged or destroyed . Perform the following procedure to verify flame current .
Remove the ignitor lead wire from the HSI terminal of the S89C ignition control .
Figure 16
Connect a shunt switch and dc micro-
Figure 17
ammeter between HS1 terminal and the ignitor lead wire .
Make sure shunt switch is closed , Figure 15 .
Turn on power to the burner . After the burner flame starts , wait at least 15 seconds , then open the shunt switch and read DC amps which must be at least 0.8 microamps DC (. 08 µ Adc ).
AC AMPERAGE
The measurement of AC amperage can be quite helpful in diagnosing problems with any of the loads found on HVAC equipment . It can help you find other problems too . Did you know that high amperage readings from motors can tell you that there is a problem with a device that is being powered ? Plugged fuel units on oilburners , dirty fans and many other problems can be initially diagnosed by knowing the start and run parameters of your motors . The easiest meter to use to do this with is the clamp around like the
Figure 18
DM3218 , Figure 2 . In Figure 16 we show the meter being used to determine the running amperage of a powerburner while in operation . In Figure 17 we show the meter being used to determine the start amperage of a motor . Starting amperages are very quick and many digital meters do not react quickly enough to capture this important reading .
Using the DM3218 , first place the meter across either power lead of the motor by opening the snap clamp button on the left of the meter . Rotate the dial to the 20A∼ac scale . Depress the M-H button . Start the motor and the highest amperage draw that the motor exerts on the meter will be shown as in Figure 17 . This reading will be held until the M-H button is depressed again .
The 81B can also be used to determine
the run and start amperages of the motor or any load device . The directions for use are as follows : Select the correct Amps Scale by rotating the center rotary scale . Keep in mind that the 81B has three amperage scales amps ( A ), milliamps ( mA ) and microamps (µ A ).
Make sure that the meter leads are in the proper meter lead terminals , 10A and COM for amps or mA and COM for the measurement of milliamps or microamps and that AC appears in the display . If not , push on the SELECT button . Do not touch the metal tips while testing and remember that in amperage testing , we must be in series with the circuit . Using alligator clips , place the meter lead probes in series with the incoming power lead to the motor , or load , and apply voltage to the circuit obtaining an amperage reading
Figure 19
from the display , Figure 18 .
Using any meter , we can also determine if there is a problem with high voltage ignition ignitors used on many powerburners today . Here the meter must be set to first determine if the current draw is within the limits that the OEM desires on the primary side of the ignitor . In Figure 18 we have placed a Victor 81B meter in series with the incoming power lead to an ignitor . By now applying power we observe that there is a power reading to the ignitor . By checking the current draw while the ignitor is running for five minutes , we should find that there should be no change during the test of more than 10 % difference . The test can be done using the amps or milliamps scale depending on the OEM ’ s preference . In Figure 19 we show an 81B placed in series with an older split-phase type motor . When using an ammeter , we can quickly determine the amperage of any load device and determine its drawing characteristics . Thanks for reading this and see ya ! l FON
George Lanthier is the owner of Firedragon Academy . His website can be found at www . FiredragonEnt . com which includes a link to Firedragon Academy ’ s Facebook page .
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